The present invention comprises a spacer element for use between the glass sheets or panels of multiglazed windows. It further comprises windows made using the spacer element.
Double or even triple glazed windows are now in almost mandatory use in new construction as an energy saving requirement. These windows normally employ two, and sometimes three sheets of glass. The individual glass sheets are separated by a molding or spacer along their edges. This molding normally is sized so that the individual sheets are in a range of about 10 to 16 millimeters apart. The interior volume of the window is sealed from the outside atmosphere to prevent entry of moisture and dust. Moisture entry, which will cause fogging on the interior surfaces, is a particularly serious problem. A number of complex systems, which often include use of a desiccant, have been developed to cope with the situation.
Another serious problem with multiglazed windows is deformation of the glass sheets due to a change in the internal gas pressure between the glass sheets as compared to the then ambient environmental atmospheric pressure. This positive or negative pressure differential can be caused by a number of factors: changes in barometric pressure, changes in temperature, or differences in normal conditions between the place of manufacture and the location of use. It is quite common that windows that are manufactured in a sea level environment are destined to be used in buildings at much higher elevations or at locations which experience severe cold during the winter. The first condition will cause a marked expansion of the gas within the interior volume of the window. The latter condition will cause a significant contraction of the interior gas volume. Expansion causes the glass sheets to deflect outwardly and become generally convex on their surfaces, rather than planar, while contraction of the interior gas causes the glass surfaces to deflect inwardly and become concave. In either case distortion is introduced when looking through the window and the building may take on a distinctly unfavorable outward appearance, especially where extensive glass curtain walls and glass spandrels are used as the exterior fenestration. These pressure changes within the windows also induce stress at the glue planes where the windows are bonded along their edges to the spacer that separates the individual glass sheets. This often causes leakage at this location during continued exterior and interior pressure equalization.
The prior art has recognized the above problems and attempted to deal with them, although not in a satisfactory manner until the present invention. As one example, Day, in U.S. Pat. No. 4,065,894, discloses a replaceable desiccant container that fits within a window frame. The desiccant is in communication with the interior volume of the window through a cannula. Preferably the container is both flexible and expandable. The inventor in this patent did not deal with the problems of where to locate the desiccant container or of providing access for replacing or servicing when the desiccant becomes saturated
The above inventor, Day, in U.S. Pat. No. 4,542,611, shows another construction having a desiccant container along the spacer gasket of one edge of a double glazed window and an expandable bladder along another edge. One side of the bladder is vented to the atmosphere. This invention deals with both the problems of maintaining interior volume dryness and of accommodating expansion or contraction of the contained gas. In addition to being of relatively complex construction, the bladder is exposed both to view and to the deteriorating effects of ambient sunlight.
Schoofs, in U.S. Pat. No. 4,455,796, provides spacer bars filled with a desiccant between the panes. The spacer bars have access to the interior volume only at their ends and access to the external environment only at their center. The inventor states that incoming air; e.g., air flowing into the internal volume of the window due to a temperature drop, is demoisturized through long columns of desiccant in the spacer bar. Outgoing air, such as when the temperature increases, is said to be dry and to strip moisture from the desiccant to maintain its efficiency.
Mondon, U.S. Pat. No. 4,604,840, provides a spacer bar construction having an internal bellows. The bellows is vented to atmosphere on the outside and exposed to the interior space on the other side. The bellows can thus expand or contract as pressure in the internal volume changes. Mondon maintains the internal volume of the window isolated from the outside environment and there is no interchange of air as in the previously noted patent to Schoofs. Certain portions of the channels may also contain a desiccant material.
Paquet, in U.S. Pat. No. 4,607,468, shows an extruded spacer bar having a hollow core. The face of the spacer oriented towards the inside of the window is a thin expandable and contractible diaphragm of a different (softer) material than the rest of the construction. The other side of this diaphragm is vented to the atmosphere. In one version a desiccant is placed in a chamber on the interior side of the diaphragm.
All of the spacer bar construction described above are quite complex and would be expensive and difficult to fabricate, maintain, and install. For these reasons they have not found acceptance within the glass and glazing industry. The need therefore remains for a construction which is simple, inexpensive, of adequate life-cycle expectancy, and highly effective at maintaining multiglazed windows moisture free and distortion free under a wide range of environmental conditions. There is a further need for a system which will provide internal pressure or volume compensation to accommodate environmental differences between the point of manufacture and the location of use.
Rigid spacer bars of metal construction not mentioned hereinbefore but which are most commonly used today, must be of a bright and light finish in order not to absorb radiant heat within the internal window volume and thereby magnify the problems of volume expansion and contraction.